Workrave

Workrave preferences

 * Micro-break: uncheck Enable timer
 * Rest break
 * Time between breaks: 1 hour 0 min.
 * Break duration: 4 min.
 * Daily limit
 * Time before end: 10 hour 0 min. (??)
 * Postpone time: 2 hours

I try never to go over this limits. Most of the time I should have taken a break long before it. If I'm prompted for a break it's a warning for me I was long due for a break.

Workrave in Ubuntu/GNOME Desktop

 * You should use the sheep in the Notification Area (where the icon for the internet connection is, too). Using the other sheep is clumsy, unfortunately it has to be somewhere on one of the two panels.

Starting your own sheep hurd
for ((a=1;a<=100;a=a+1)); do workrave& done Warning: It will probably be fastest to restart to get rid of all the sheep.